This invention relates generally to a device for selectively holding and releasing lines and more particular to a device for releasing reefing lines on parachute canopies or the like.
The use of parachutes, either for air dropping heavy payloads or decelerating high speed aircraft, requires the incorporation of suitable means to regulate the opening of the parachute canopy. If not regulated, deceleration of the payload caused by rapid parachute canopy opening is excessive, imposing potentially destructive forces on the attached payload. Additionally, for payloads delivered using multiple parachutes, the opening of each parachute must be controlled so that no single parachute interferes with, or "starves", the opening of the remaining parachutes. To control the opening rate of such parachute canopies, so-called reefing lines are employed, typically encircling the rim of the parachute canopy. The reefing line ends are held by a dereefing device and the reefing line is sized so that the parachute canopy cannot fully open as long as the reefing line ends are held. The dereefing devices are associated with timers or barometrically controlled devices, which after a given time or at a given altitude release the reefing line ends, enabling full opening of the parachute canopy. Multiple differently sized reefing lines may be used for each parachute canopy, with each reefing line released sequentially so that the canopy can be opened in controlled stages, allowing further control over payload deceleration.
When the canopy is opened it imposes a force on the reefing line which is transferred to the reefing device. In known dereefing devices, this force tends to hold or lock the parts of the device together. Thus, known dereefing devices must be capable of overcoming the locking force created by taut reefing lines to ensure release of the reefing line ends.
Dereefing devices can generally be classified into either destructive or nondestructive types. The destructive types include those using explosive charges or mechanically actuated blades to sever the reefing line. While destructive dereefing devices are less susceptible to reefing line loads, they do not allow reuse of the reefing line and/or the dereefing devices themselves. Nondestructive dereefing devices typically capture a reefing line end loop around a pin. The pin is releasably held within a yoke. The pin is withdrawn from the yoke to release the reefing line and loops. As previously discussed, this arrangement allows the taut reefing line to hold or lock the pin to the yoke.